1. Field of the Invention
The present invention relates to a lid for a container, and in particular to an easily removable lid and a method for manufacturing such a lid.
2. Description of the Related Art
Lids for containers such as paint pots have to be fitted tightly to the containers to avoid leakage of the contents and to reduce the chance of the lid detaching from the container in the event of deformation (e.g. as a result of being dropped). However, if the lids are fitted too tightly they become difficult to remove.
Containers such as paint cans are traditionally made from metal (typically steel) and are fitted with metal lids. The lids are generally planar with a downwardly projecting circumferential portion for engagement with a can. That projecting portion forms an interference fit within the rim of the can. Once fitted, the diameter of the lid above the rim and the diameter of the lid below the rim are greater than that of the aperture provided by the rim. Thus, to secure the lid and ensure a good seal between the container and the lid, force is required to insert or remove the lid. As a result, removal of the lid generally requires the use of a levering tool such as a screwdriver to be inserted between the container and a flange on the lid and prying the two apart.
As an alternative to the metal can, paint containers have recently also been made from plastic. If desired, the containers can be made from transparent plastic so that consumers can see the contents of the container. The lids of these containers are also made from plastic. Unlike the metal lids, they are provided with a groove that engages with a projection inside the rim of the container. However, they are removed in a similar manner to the metal lids. A tool is used to prise the lid from the container, the projection being deformed and forced from the groove as the lid is removed.
It will be appreciated that with such lids a compromise is necessary between making the lid fit tightly and being able to remove it with the aid of a tool such as a screwdriver. This means that the lid may not be secured as well as would be ideal with a consequent risk of spillage of paint. In addition, the need to use a tool to remove the lid is disadvantageous.
Screw top lids would not have these disadvantages, but they have been found to be unsuitable for containers for paint because the threads become clogged with paint and the lids are then very difficult to remove.
Lids may be provided with a seal around the edge to prevent leakage of the contents of the container. The seal may be made from rubber or other suitable flexible polymers. When a tool is used to remove the lid from the container, this seal frequently gets damaged. This can be a problem when the container needs to be opened after it has been filled in the factory and before it is sold to the end user. This is necessary when, for example, the user wants paint mixed to a certain colour. In this process, a container of neutral paint is opened, tinter is added, the lid is replaced and the container is then vibrated to mix the paint. It will be appreciated that, if the rubber seal is damaged in this process, the risk of the contents leaking is greatly increased.